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post #151 of 200 Old 07-09-2017, 11:55 AM
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You can look up and post whatever you like and it will add to the fun and be entertaining, but Notnyt and I have already read all "RickJames" posts and done some comparison work to show the tone, wording, phrasing, style and overall message are the same from both accounts. And there's actual irrefutable evidence from a networking perspective.

If you could do more of the same that would be helpful, but I think we've already nailed him to the wall with abundant evidence. So it's up to you.

But this right here is what is needed. Outrage from the community and speaking out about it. Tell your friends (especially forum friends), tell your mom, tell your mechanic, tell everybody. Send people links to this thread. This is important. This thread is getting a number of hits but it's only a few people following. Everybody needs to know. I started a thread about it at diyaudio but it got locked down pretty fast. Locked but not deleted, which I take as a sign that they condone the message but can't support it, probably because it's not documented to be happening over there right now, it could cause too much emotions, or maybe it's even a liability issue.

But it's true.
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post #152 of 200 Old 07-09-2017, 11:56 AM
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Quote:
Originally Posted by Gorilla Killa View Post
Is the amount of resonance because of the driver? If you took the 40" u baffle and put a back on it, and made it either sealed or ported, why is it not subject to the same issues or am I not understanding the cause of the resonance
Quote:
Originally Posted by diy speaker guy View Post
It's not the driver, it's the open back box. Any cavity (box with a hole) will have a resonance. In a ported box that resonance is a benefit, it's tuned to where you need it to boost up the bass. But in a bad design (like a deep open back box) that resonance is right smack where you don't want it.

If you closed the box to make it sealed, the box would still have a resonance but it fits in and doesn't stick out like a sore thumb for a few different reasons, one of them being that the back wave is contained in the box.

Just think transmission line. Everyone knows those have a series of really strong resonances if unstuffed. That's the same thing that happens in an open back box because it IS a short transmission line. The box shape and depth determines where the resonance will be, and in this case, at 40 inches deep it puts the resonance at about 55 hz, and it's a STRONG resonance.
Quick sanity check to help Gorilla Killa and others follow along more easily. I don't have time at the moment to tinker with hornresponse, but there are probably 3-4 ways you could model something comparable. Understanding what you are looking to confirm is what really matters. Ultimately the install you described radiates sound into the room like any sealed subwoofer, meaning all sound is produced directly by the cone motion, and no other sources. In simple terms this is a driver with a 40" deep manifold/straight section connected to a large sealed space on the rear. The only question that needs to be answered is if 40" is too deep for the cross section of the manifold? "Too deep" is defined as creating notches or undesirable loading on the driver.

The quick/easy method would be to model the system looking from the rear side into the room. This has already been posted by others. This puts the microphone in the rear room with the straight pathway in front of the driver loading a 2pi-1pi condition and the listening space as the rear, near IB, back box. Look at the driver excursion, as that determines your in-room SPL. If there is a big notch in the passband, start making adjustments to push that above the passband. That will mean either a shorter or larger area manifold. You could also move the drivers 1/2 way between to shift the loading an octave higher, but now you have both sides resonating in unison. I suspect placing the drivers about 60%, or 24", from the listening side would offset the resonances and make the listener side resonance higher. Also remember that the higher in frequency you can push the resonance, the more some resistive stuffing would reduce the effect.

You have identified the potential issue in loading the drivers as described, now you just need to determine a reasonable solution. I do like the dual-opposed configuration where you could eliminate mechanical forces, while also pushing the acoustic location back into the depth of the 40" distance. Add a suitable layer of fiberglass or cotton to the rear opening and be sure it's held in place with mesh fabric or screen, and you should have a very potent result. Of course before building I would find any sealed subwoofer available to measure and confirm the front/center location is a useful one in your room.

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post #153 of 200 Old 07-09-2017, 12:06 PM
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Quote:
Originally Posted by Mark Seaton View Post
Quick sanity check ...
Not sure how much of this you've read but I've already gone through all this point for point already, so obviously I agree with you. Thanks for stopping by.

Quote:
That will mean either a shorter or larger area manifold.
Or H baffle or W baffle, both of which have been simulated (but only one variation of each).

Quote:
You could also move the drivers 1/2 way between to shift the loading an octave higher, but now you have both sides resonating in unison.
You are describing the H baffle I simulated.

Both sides resonating in unison is actually a huge benefit. It means the sound will be the same on both sides so eq can fix any issues. Also, he uses both rooms so it would be good to be able to use this sub FOR both rooms.

We've already discussed stuffing and measuring the room gain curve with a simple sealed sub.

So basically I agree with everything you've said (I should since I've already said it) with the small caveats here to add to your post.

Thanks.

One thing I haven't mentioned yet is that I CAN design it to eliminate the resonance peak altogether, if that's desired. It's easy enough. I've only shown one variation of the U, H and W baffle so far but I could design it for a very flat response.
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post #154 of 200 Old 07-09-2017, 12:26 PM
 
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Quote:
Originally Posted by diy speaker guy View Post
You can look up and post whatever you like and it will add to the fun and be entertaining, but Notnyt and I have already read all "RickJames" posts and done some comparison work to show the tone, wording, phrasing, style and overall message are the same from both accounts. And there's actual irrefutable evidence from a networking perspective.

If you could do more of the same that would be helpful, but I think we've already nailed him to the wall with abundant evidence. So it's up to you.

But this right here is what is needed. Outrage from the community and speaking out about it. Tell your friends (especially forum friends), tell your mom, tell your mechanic, tell everybody. Send people links to this thread. This is important. This thread is getting a number of hits but it's only a few people following. Everybody needs to know. I started a thread about it at diyaudio but it got locked down pretty fast. Locked but not deleted, which I take as a sign that they condone the message but can't support it, probably because it's not documented to be happening over there right now, it could cause too much emotions, or maybe it's even a liability issue.

But it's true.
It's a standing offer.

I agree, its now black and white, but if his supporters start to chime in, I've got irrefutable math, that he railed against, then went dark, then arrive with Rick James, and on more than one occasion / thread.

I will remain watchful, and reference them if the need arises, such as either Bill or Rick James making further claims that they're not one in the same, or where Rick James unabashedly praises/supports Bill, etc...

returning to fly on wall!

Cheers
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post #155 of 200 Old 07-09-2017, 02:23 PM - Thread Starter
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@notnyt , if I didnt have the drivers already I would do the big ported. When I bought these, I was set on doing IB and I didnt consider these are only going to work in this configuration. I could sell them at a loss, if I cant get it to work that will be on the table.

When you put the LMS on the block lemme know lol



I have 4 other subs in the room with 2 of them upfront on each side of the screen. I have a good response ie no phase issues nulls, a peak at 30 hz down which I eq'd in. The rear of the closet is load bearing so its a no-go modifying it in any way. The depth was in a effort to get the drivers close to bottom of the screen and keeping the room in tact and avoid in possible issues that could arise with the semi enclosed closed closet.



Quote:
Originally Posted by diy speaker guy View Post

One thing I haven't mentioned yet is that I CAN design it to eliminate the resonance peak altogether, if that's desired. It's easy enough. I've only shown one variation of the U, H and W baffle so far but I could design it for a very flat response.
If you have something in mind Im open to suggestions. wings What Im think Im going to do is build it as it needs to be and if the closet seems to cause a issue, take the walls down. The 2 end walls are 14" and the center divider is 17". I attached the drawing again if its needed.

I have subs in my room behind the theater honestly dont care if its usable in that room. I will add it can be taller if this helps. The dual opposed like @LTD02 put up, is that along the lines of what you have in your sims.
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post #156 of 200 Old 07-09-2017, 02:37 PM
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LTD's most recent drawing? No, I simulated that [edit] hasn't been simulated yet [/ edit], it still retains the big resonance problem.

I still haven't entered your actual driver specs into the sim, I've been doing everything with the same size box (whether it be U, H or W baffle) with the dimensions you provided in post 1 for the purpose of making all my sims directly comparable. Same size enclosure, same shape (overall), same power level, same drivers. The only difference is in the baffle wall itself, U, H, W shape.

I haven't done any tweaking to the sims to get the best possible response for a few reasons.

1. I haven't entered your driver t/s yet.
2. I don't know what you are going to do with the closet. Leave it? Tear it out?
3. I don't know your max dimensions and what you are willing or able to do to the house to make this happen.

You say you can't mod the rear wall of the closet at all - does it already have a hole in it?

What the max size of the "enclosure" that you can deal with? I'm going to need exact dimensions. A lot of this will depend on how big the existing hole in the wall is (if there is one), how many drivers you want per "enclosure", stuff like that.

I can get you a nice response but again, it would be better if you could measure you room gain curve FIRST so I can incorporate that into the sim. If you need help with that I can help you. And I need to know what kind of eq you have if any. Full dsp is always nice, and may or may not be required depending on what the room does to the response. As Vince said, it's not much use designing for a perfectly flat response if the room is going to shred it.

Another thing that hasn't been mentioned is that you can use a resonance peak at the top of the passband to very good advantage as Ricci has done with his MAUL and SKHorn designs. In that case you deliberately design a big fat peak into the response at/near the top of the passband and eq it down to flat. That give you less power needed in the eq'ed frequencies which is beneficial for a number of reasons.

How fancy do you want to get? Can you measure the room gain curve? Do you want extra sensitivity at the top of the passband so you can eq it down and make life easier on your drivers and amps? Are you absolutely sure you never will want to use the sub for both rooms on both sides of the wall? If not, why not? That's one of the biggest advantages to IB. Lots of questions before I start even thinking about doing final sims for you.

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post #157 of 200 Old 07-09-2017, 02:40 PM
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I can also sim your drivers for large ported if you want. If you have enough space it can work, the boxes will be large. And if you have full dsp you can make almost ANYTHING work.

Those drivers would also be comfortable in huge sealed boxes too, which is just one step away from IB.

Lots for you to think about. Hit me with your best game plan and let's go from there.
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post #158 of 200 Old 07-09-2017, 02:58 PM
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Just for reference, IMO, by far the best sim posted is the H baffle in post 123. There's no mechanical force cancellation but the benefits in frequency response are tremendous, at least compared to the U baffle we started with.

If IB is what you want I think H baffle is the way forward and I can tweak that sim once you answer some of the questions I asked.

I can also sim large sealed and large ported, it doesn't take me long - just a couple of minutes per sim - but if you want ported I need to know the max size and dimensions you can handle and the lowest frequency you want to hit. There's a big difference between designing for 5 hz and 20 hz.

For that matter i can even give it a whirl in a tapped horn but it will be monstrously large.
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post #159 of 200 Old 07-09-2017, 03:45 PM - Thread Starter
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Thats a lot to take in. Ill have some answers for you in a few days as you have given more to think about.
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post #160 of 200 Old 07-09-2017, 03:49 PM
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Quote:
Originally Posted by diy speaker guy View Post
This doesn't solve the problem of the 40 inch U baffle - you just put the drivers on the side of the 40 inch U baffle.

The H baffle reduces the depth to 20 inches (per side). To fix the problem you HAVE to make the cavities less deep and/or horn shaped.

So with these pictures now we have the same response as before but with an addition problem at 150 hz due to the driver being offset in the tunnel.



au contraire mon frère.


an assumption underlying your method is infinite space on the back side of the driver, but what I have shown is the same size horn attached to the backside of the wall.


as a result, each side of the driver will see the one "front loading" + one "rear loading"--remember that is half of the what makes the H-frame work (the other piece being the shortened horn sections).


as was shown previously, when you combine those two effects, the curve smooths out dramatically leaving only some beneficial increase in efficiency. the increase in sensitivity will apply to both sides of the i.b. and so it can be eq'd out if desired.






what you have modeled is something like this, no?





where what I drew up is something more like this:





so the net behavior would be closer to the H frame subwoofer that we had discussed previously, but with the full 40" of length on each side.


of course, this picture is for one sub and is rotated, but conceptually the same as the sketchup drawing.


no?
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Listen. It's All Good.

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post #161 of 200 Old 07-09-2017, 05:02 PM
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Quote:
Originally Posted by LTD02 View Post
what you have modeled is something like this, no?





where what I drew up is something more like this:


Yes you got me. I made a major boo boo. I can't even believe I did that. It's so obviously wrong in so many ways I should have caught it, or rather not done it in the first place.

I have some stuff I can't leave unattended but I'll clean up my mess asap, maybe delete the post in question so it doesn't cause any confusion. Yes, your drawing would be like the second example here.

Thank you for pointing it out, I hate making stupid mistakes, hate even more when they go undiscovered. That's the second time you caught me making errors in this thread, I appreciate someone keeping an eye on me. I'd much rather be wrong and correct it than to put misinformation out there.
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post #162 of 200 Old 07-09-2017, 05:11 PM
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if it isn't clear how one gets from the simple model to the sketchup drawing, attached images show it one step at a time.
rotate the model 90 degrees.
shift it to the right
make a copy and flip it vertically
remove the panel down the middle of the horn
make another copy
fill in the baffle wall ends
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post #163 of 200 Old 07-09-2017, 05:26 PM
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but you didn't explain how that little guy got in there and why he's straining to hear four 18s - that's the big mystery - he does look like a happy little guy though
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post #164 of 200 Old 07-09-2017, 08:59 PM
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Ok, I deleted and edited the 3 posts that contained references to my mistake. The only one missing is LTD's which is fine because he makes it clear that the sim is wrong.

Here's the updated sim. A compound horn can only have 1 segment on the front horn so I can't sim the offset, same as with the W baffle but here's the result. The only thing missing is the offset which would give a deep notch at about 175 hz or so. Response will be the same in both rooms because it's symmetrical. Keeping with the same theme this is shown with same same overall volume, same drivers, same power level as all previous sims. The benefit (when configured as drawn in post 135) is that you do get mechanical force cancellation. The consequence (if it is to be considered a problem) is the peak shifts lower in frequency than the 1/2 depth H baffle in post 123. But as mentioned, that peak can easily be eq'ed down and the extra sensitivity in that range would actually be good for the drivers and amps. A possible problem might be that the deep notch that the offset drivers will produce at 175 hz might be too close to the passband and mess things up a bit. I'd have to use Akabak for that.

I still prefer the H baffle in post 123 so far.

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post #165 of 200 Old 07-10-2017, 07:54 AM
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Well, it's been over 24 hours, and it looks like RickJames won't bite. It's like getting a German spy to say "squirrel". Here are all the proper answers that would have proved, without a doubt, that he was Quebecois. Maybe it'll help anyone who's planning a visit, (like maybe for the next Formula 1 Grand Prix!) with unique insights into Canadian culture...


1. What would you call this? Click image for larger version

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Un depanneur.

2.What would you call this? Click image for larger version

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A toque.

3. What is the correct way to serve fries?
Smothered in gravy and cheese curds. Not even cheese... cheese curds. You must also drizzle any other rendered meat fats at your disposal (preferably bacon fat) over the top for garnish and to help melt the curds. Meh, whatever... we've got free health care.

4. What do you do on your anniversary?
Trick question - which anniversary? Your wife's? Your mistress'? Which mistress?

5. When you see a traffic signal turn yellow, that means...
There's only time for a maximum of 10 - 15 more cars to pass. I would also accept "Ooh cares, hein? 'Dere's nobody 'ere anyway."

6. Correct following distance behind a car going 100km/h?
Trick question, not even school buses go that slow. However if you do come upon a tourist, one must give a minimum of 3 inches clearance in dangerous conditions so as to be extra considerate.

7. At what temperature do your testicles start to freeze when you're wearing jeans?
Trick question, all Canadians have balls of steel.
(Fun fact: Jeans will freeze solid at about -25*C or below, even when they are dry!)

8. What do you say when you hit your thumb with a hammer?
Tabernac! Partial points for merde or ****. Canadians are bi-lingual, eh?
(Fun fact: It's the law in Quebec that if you swear at somebody in the street you have to do it in both languages so as not to offend them.)

Be aware while you're visiting that Canadian legal sentences can be quite harsh. Minor offences can sometimes be dealt with by walking the several blocks to the North Pole to get ice for everybody's beer.

I was going to include one more:
9. While crossing the street, you get hit by a car. What do you do?
Immediately apologize for damaging the car, make sure the driver is OK, then go to the hospital for free health care... after stopping for some Timbits together. "Hey, I was goin' to Tim's, too!"

But that would have only proven he was from Canada.


As for you, RickJames, you have just proven you are not my buddy, friend.

Here is an informative video to reinforce and expand on my points for those that want to "blend in". We welcome one and all.


And mandatory:


Happy belated 150th, everyone!

--------------------------------------------------------------------------------------------------------------
Subs are like pizzas: you get way more good stuff with the big ones.
https://www.avsforum.com/forum/155-di...uxl-build.html
https://www.avsforum.com/forum/155-di...-overture.html

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post #166 of 200 Old 07-10-2017, 02:55 PM
 
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Quote:
Originally Posted by bimmaguy View Post
Well, it's been over 24 hours, and it looks like RickJames won't bite. It's like getting a German spy to say "squirrel". Here are all the proper answers that would have proved, without a doubt, that he was Quebecois. Maybe it'll help anyone who's planning a visit, (like maybe for the next Formula 1 Grand Prix!) with unique insights into Canadian culture...


1. What would you call this? Attachment 2227809

Un depanneur.

2.What would you call this? Attachment 2227817
A toque.

3. What is the correct way to serve fries?
Smothered in gravy and cheese curds. Not even cheese... cheese curds. You must also drizzle any other rendered meat fats at your disposal (preferably bacon fat) over the top for garnish and to help melt the curds. Meh, whatever... we've got free health care.

4. What do you do on your anniversary?
Trick question - which anniversary? Your wife's? Your mistress'? Which mistress?

5. When you see a traffic signal turn yellow, that means...
There's only time for a maximum of 10 - 15 more cars to pass. I would also accept "Ooh cares, hein? 'Dere's nobody 'ere anyway."

6. Correct following distance behind a car going 100km/h?
Trick question, not even school buses go that slow. However if you do come upon a tourist, one must give a minimum of 3 inches clearance in dangerous conditions so as to be extra considerate.

7. At what temperature do your testicles start to freeze when you're wearing jeans?
Trick question, all Canadians have balls of steel.
(Fun fact: Jeans will freeze solid at about -25*C or below, even when they are dry!)

8. What do you say when you hit your thumb with a hammer?
Tabernac! Partial points for merde or ****. Canadians are bi-lingual, eh?
(Fun fact: It's the law in Quebec that if you swear at somebody in the street you have to do it in both languages so as not to offend them.)

Be aware while you're visiting that Canadian legal sentences can be quite harsh. Minor offences can sometimes be dealt with by walking the several blocks to the North Pole to get ice for everybody's beer.

I was going to include one more:
9. While crossing the street, you get hit by a car. What do you do?
Immediately apologize for damaging the car, make sure the driver is OK, then go to the hospital for free health care... after stopping for some Timbits together. "Hey, I was goin' to Tim's, too!"

But that would have only proven he was from Canada.


As for you, RickJames, you have just proven you are not my buddy, friend.

Here is an informative video to reinforce and expand on my points for those that want to "blend in". We welcome one and all.

https://www.youtube.com/watch?v=EsL_TAfQxH8

And mandatory:

https://www.youtube.com/watch?v=pASE_TgeVg8

Happy belated 150th, everyone!
The sad part is or perhaps merely laughable aspect of your post is that it's all more or less true... I had a good laugh.

Thanks for the posts!
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post #167 of 200 Old 07-10-2017, 04:26 PM - Thread Starter
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Quote:
Originally Posted by LTD02 View Post
if it isn't clear how one gets from the simple model to the sketchup drawing, attached images show it one step at a time.
rotate the model 90 degrees.
shift it to the right
make a copy and flip it vertically
remove the panel down the middle of the horn
make another copy
fill in the baffle wall ends
Is the final image to scale from the sim? The 2 end baffles with the rear wave are narrower than the manifolds with the drivers facing. I ask so I can figure if theres space. The depth of the drivers wont allow for in between stud spacing where the drivers are facing each othere Id have to be 32" spacing on those to accommodate.

Also this might be important, the wall is load bearing so removing or cutting any studs in that wall is not an option. That would put a stud in the middle of the mouth of those 2 manifolds.
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post #168 of 200 Old 07-10-2017, 05:05 PM
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Originally Posted by Gorilla Killa View Post
Is the final image to scale from the sim? The 2 end baffles with the rear wave are narrower than the manifolds with the drivers facing. I ask so I can figure if theres space. The depth of the drivers wont allow for in between stud spacing where the drivers are facing each othere Id have to be 32" spacing on those to accommodate.

Also this might be important, the wall is load bearing so removing or cutting any studs in that wall is not an option. That would put a stud in the middle of the mouth of those 2 manifolds.

i tried to get close to what you asked about in the sketchup drawing (main section manifolds are 40" wide x 24" tall and 40" deep).


each driver gets 20" of width, so where you have a dual driver, that manifold would be 40" wide. each manifold with a single driver is 20" wide.


having studs in front of a section will change things a bit, but i don't think it would change things enough to worry about it. kind of similar to having bracing in the mouth of a horn.


I don't quiet understand what you mean with respect to driver spacing and the studs and 32" spacing. if the manifold will be built in between the permanent wall and the theater room, all four drivers could be loaded from the theater side.

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post #169 of 200 Old 07-10-2017, 05:10 PM
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@diy speaker guy
why did you reduce the manifold area in post 164?
the sketchup shows roughly 20" width x 24" height (~3100 cm^2) for each driver, 12400cm^2 total, which is what i was working with from your earlier models.


I've drawn a 'rough guess' at the effect of the offset driver cancellation at 175hz.




this is what is creating that dip:







what happens to all these resonances if one sticks a couple of pillows in the manifolds?


can we see that in hornresp?









would it kill both the cancellation as well as the gain?


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post #170 of 200 Old 07-10-2017, 06:05 PM
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@diy speaker guy
why did you reduce the manifold area in post 164?
the sketchup shows roughly 20" width x 24" height (~3100 cm^2) for each driver, 12400cm^2 total, which is what i was working with from your earlier models.
I had to chose - something had to give. Your path length was 2x longer than my H baffle sim so I either had to use 2x more volume in the "enclosure" or make the paths narrower and keep the total volume the same. I chose the later. It was an arbitrary choice, but I was trying to keep my series of sims with some commonalities to make them directly comparable - I've gone to some lengths to make sure all my sims have the same "enclosure" volume. I think it's 1264 liters total. In order to do that I had to reduce the frontal exit area by half, which is no consequence because in your drawing the frontal area is actually the same but some of it is blocked off by the cavity boundary from the cavity on the other side.

Quote:
I've drawn a 'rough guess' at the effect of the offset driver cancellation at 175hz.
That is actually a very good guess, I'd be surprised if Akabak came back with results that are significantly different than that. Good job.

Quote:
this is what is creating that dip:
Correct. The sound bounces off the closed end, comes back and recombines but time delayed so out of phase, and 180 degrees out of phase at 175 hz specifically.

Quote:
what happens to all these resonances if one sticks a couple of pillows in the manifolds?
Depends on the specific resonance you are talking about. Very narrow sharp resonances are easy to kill, in fact due to natural losses inside the enclosure an extremely narrow predicted spike might not show up in real life at all. But once you get into resonances that are an octave wide it will take a massive amount of dense stuffing to do much to them other than round off the peak a bit.

Quote:
can we see that in hornresp?
You can add stuffing in Hornresp, yes. I helped David a few years ago by doing a couple hundred MJK sims so he could correlate the results and add the stuffing feature to ALL enclosures, not just sealed boxes. I've never used the stuffing feature, I pretty much know what's going to happen with stuffing anyway. It's not going to be very effective on some of the wide resonances we're seeing. But eq will be effective, which is why it's nice to have a symmetrical "enclosure" so eq applied will fix issues on both sides.

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post #171 of 200 Old 07-10-2017, 06:23 PM
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Here's how to do stuffing - do it in the loudspeaker wizard, go to "filling", use the sliders to indicate where and how dense you want it and it will report how much polyfil is required to correspond to the sim.



The problem is that you can't do an offset sim with a CH (compound horn), which is what we've been doing. The front horn only has one segment available so it can't be offset. And if you select CH you can't also select OD for the back horn either.

So you can view the effect of stuffing but not in the designs we have been discussing. If you want to sim it as above (like the incorrect sim I posted earlier with no U baffle on one side) you can look at the resonance and cancellation notch and see how stuffing will affect it but it's not an accurate representation of the enclosures we've been discussing. But you can learn how various positioning and densities of stuffing will impact a resonance and a cancellation notch.

I'm also working on getting Leonard Audio TL.app going on these, it actually can sim this stuff, offset drivers with stuffing and all.

I've been avoiding Akabak because I don't have an Akabak computer right now and I'm not going to run a virtual environment on this particular computer.

Have you used TL.app? I've actually already completed a sim but it's slightly different than Hornresp.
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Originally Posted by diy speaker guy View Post

Correct. The sound bounces off the closed end, comes back and recombines but time delayed so out of phase, and 180 degrees out of phase at 175 hz specifically.

Depends on the specific resonance you are talking about. Very narrow sharp resonances are easy to kill, in fact due to natural losses inside the enclosure an extremely narrow predicted spike might not show up in real life at all. But once you get into resonances that are an octave wide it will take a massive amount of dense stuffing to do much to them other than round off the peak a bit.
Narrow bandwidth spikes in output will show up in real life and rear their ugly head in the time domain measurement, and will ring like a bell.

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Depends how narrow you are talking about. If they are VERY narrow the peak will be rounded right off and most if not all of the spike won't show up in real life. I'm talking about narrow, like maybe 5 pixels wide or less in the Hornresp sim. Danley mentions this several times over the years.

But if they are not EXTREMELY narrow just a bit of the top of the peak gets rounded off by naturally occurring losses in the enclosure, most of the resonance remains and it does act as you describe.

It all depends on how narrow and tall the spike is in the first place.
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@diy speaker guy
re: stuffing.
thanks. i thought it would make more of a difference than it did.

putting all the pieces together, it would seem that something like a dual-opposed-expanded-H-frame would be about ideal (if it is workable in the environment).










with this one, the benefits are no cancellation (well, since it is symmetrical the cancellation is actually occurring right on the peak which brings it down somewhat), a little rise in efficiency in the upper bass, and vibration cancellation.


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@diy speaker guy
re: stuffing.
thanks. i thought it would make more of a difference than it did.
Yeah, it's hard to do much of anything to a wide resonance or dip. If you don't want it, it's best to eliminate it by design, not by lossy losses like stuffing after the fact. Stuffing should only be applied sparingly as a final tweak to a system IMO.

Quote:
putting all the pieces together, it would seem that something like a dual-opposed-expanded-H-frame would be about ideal (if it is workable in the environment).

with this one, the benefits are no cancellation (well, since it is symmetrical the cancellation is actually occurring right on the peak which brings it down somewhat), a little rise in efficiency in the upper bass, and vibration cancellation.
That's a nice looking response, easy to work with and symmetrical so eq can be used to good effect. Also force cancellation and it looks good too.

Hopefully OP can still measure the room gain curve, that might change things a lot. I'm waiting on him to give me answers to the stuff I asked yesterday before I even attempt to do any final sims.

Anyway, you didn't mention if you have ever tried Leonard Audio TL.app. It can sim all this stuff, offset drivers, tunnels on both ends of the driver, stuffing, all of it.
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post #176 of 200 Old 07-10-2017, 10:37 PM
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Also your cancellation notch is going to be much higher in frequency since the center of the driver is only about 24 cm from the closed end of the tunnel now. So that notch won't really be any kind of problem, it'll be way above the passband now. Many benefits to this particular design, LTD.
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post #177 of 200 Old 07-10-2017, 10:56 PM
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The only thing is that I wouldn't call that an H frame. It's more like a W but with flattened ends and steps instead of a linear expansion.
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post #178 of 200 Old 07-11-2017, 04:12 AM
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@diy speaker guy
thanks, and no, i haven't taken a look at the Leonard Audio TL.app.


good thread.

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post #179 of 200 Old 07-11-2017, 07:22 AM
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I'll post a sim using tl.app much later today so you can see it in action.

It's easy to use but way different than Hornresp as far as GUI. It also produces slightly different results but not so different as to be unusable. It's also not as stable as Hornresp and the tapped horn feature doesn't give accurate results, but everything else is fine. I'll do a comparison sim later and show how it works and you can decide if it's something you want to look at.

I've got a bit of a history with that program too, I was there as it was being written (not in personal obviously, but on the forum) so I had some input on how it turned out and I also wrote about half of the user manual.
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Quote:
Originally Posted by diy speaker guy View Post
Just for reference, IMO, by far the best sim posted is the H baffle in post 123. There's no mechanical force cancellation but the benefits in frequency response are tremendous, at least compared to the U baffle we started with.

.
I'll take mechanical force cancellation and EQ if I had to choose.

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